Changing in game and client language in NA

Hello every one! I am currently playing on the NA server, and my goal is to have the game completly in french. I've tried many options from videos on youtube and guides online (changing local from en_US to fr_Fr, or adding options to my regions folder),they do make the first two login screens french,but my login it self fails everytime.

If anyone has an updated solution that could help menplease let me know, thanks!